The invention relates to electronic devices, and, more particularly, to circuitry and methods for conversion of sampling rates of digitally sampled data.
Audio systems currently are required to handle data with various sampling rates, from low rates found in many .WAV files such as 8 kHz to high rates of consumer audio equipment such as 48 kHz. Audio is a key feature of PC multimedia with system requirements approaching those of consumer high fidelity systems for a fraction of the cost. For example, the PC 2001 specification sets high quality audio requirements to play out audio streams at 44.1 and 48 kHz rates. A hardware vendor may choose to supply a codec that only supports 48 kHz. In this case, sample rate conversion between 44.1 and 48 kHz is needed.
T. Ramstad, Digital Methods for Conversion between Arbitrary Sampling Frequencies, 32 IEEE Tr.ASSP 577 (1984) presents a general theory of filtering methods for interfacing time-discrete systems with different sampling rates. This includes time-varying filter coefficients derived as various interpolations samples of a windowed ideal impulse response function. And U.S. Pat. No. 6,141,671 discloses an asynchronous sampling rate converter with the time-varying filter coefficients as linear interpolations of samples of a windowed ideal impulse response function plus input/output clock tracking by comparisons to a master high frequency clock.
However, the known sampling rate converters have computational complexity or clock jitter sensitivity.